1. Field of the Invention
The present invention relates to a developing device in an image forming apparatus such as a copying machine or a printer and the like employing recording system such as an electrophotographic recording system or an electrostatic recording system and the like, and to a process cartridge on which such developing device is mounted.
2. Description of the Related Art
In an image forming apparatus in which images are formed on a recording sheet using developer such as toner and the like, various measures are taken for preventing leakage of developer in order to improve quality of the apparatus.
Especially, in developing units containing developer, or in an apparatus in which a unit of a photosensitive member and a developing unit is replaceable, vibrations are generated not only during operation of the image forming apparatus, but also during replacing operation. As a consequence, developer is liable to leak, and thus more reliable countermeasure against leakage is required. In particular, developer is liable to leak from the portion of the developing device container where a developing roller is disposed since there is formed an opening for supplying developer to the photosensitive member. Therefore, various measures for preventing leakage of developer through such opening have been proposed.
For example, a cartridge as proposed in JP-A-2000-284589 includes an end portion sealing member disposed at the longitudinal ends of a developing roller along the periphery of the developing roller in order to prevent leakage of developer from the longitudinal ends of the developing roller and a flexible sheet member (spurt preventing sheet) for preventing spurt of toner from a gap formed between the developing roller and the developer container along the length of the developing roller.
The end portion sealing member is a member having a multiple layer structure including a surface layer formed, for example, of non-woven fabric such as PTFE, nylon, rayon and the like, or of felt or pile fabric and the like, and a cushioned base layer member such as sponge and the like bonded together with double-face adhesive tape or the like.
The flexible sheet member is formed, for example, of resin sheet such as PET and the like, which is fixed at the opening of a developing frame body at one end and is free at the other end and comes into contact with the peripheral surface of the developing roller longitudinally along almost the whole area thereof.
A longitudinal length of the flexible sheet member is such that it extends to the position that can overlap with the end portion sealing member, which allows toner that was not developed and returned into the container to pass under the opening, and prevents toner from spurting out therefrom.
However, it has been desired to further improve sealing capability because of the influence of reduction of the diameter of toner for improving picture quality, a high-speed sliding movement of the developing roller and the end portion sealing member as a result of speeding-up of image output, and elongation of life of the developing device.